JP2009221582A - Ferritic stainless steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferritic stainless steel material which has sufficiently improved thermal fatigue characteristics compared to a conventional one. <P>SOLUTION: The ferritic stainless steel material has a composition which comprises, by mass%, more than 0.000 to 0.030% C, more than 0.00 to 1.00% Si, more than 0.00 to 1.50% Mn, 15.0 to 25.0% Cr, 1.00 to 4.00% Mo, 1.00 to 5.00% Co, more than 0.000 to 0.030% N, and the balance Fe with unavoidable impurities, so as to satisfy any of the conditions expressed by the following expressions of (1), (2), (3) and (4). A content ratio of Cr, Mo and Co with respect to the total mass of the ferritic stainless steel material satisfies further a particular condition. The expressions are:(1) 0.25×W<SB>Cr</SB>+0.30×W<SB>Mo</SB>+0.60×W<SB>Co</SB>≥6.2 (here, W<SB>Cr</SB>≤20, and W<SB>Co</SB>≤3.0); (2) 0.25W<SB>Cr</SB>+0.30×W<SB>Mo</SB>-0.10×W<SB>Co</SB>≥4.1 (where, W<SB>Cr</SB>≤20, and W<SB>Co</SB>>3.0); (3) 0.15×W<SB>Cr</SB>-0.30×W<SB>Mo</SB>-0.60×W<SB>Co</SB>≤1.8 (where, W<SB>Cr</SB>>20, and W<SB>Co</SB>≤3.0); and (4) 0.15×W<SB>Cr</SB>-0.30×W<SB>Mo</SB>+0.10×W<SB>Co</SB>≤3.9 (where, W<SB>Cr</SB>>20, and W<SB>Co</SB>>3.0)(in the expressions (1) to (4), W<SB>Cr</SB>, W<SB>Mo</SB>, W<SB>Co</SB>represent each content amount (unit: mass%) of Cr, Mo, Co respectively in the total mass of the ferritic stainless steel material). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ferritic stainless steel material.

  In use, members exposed to a heat cycle environment that repeatedly rises in temperature from normal temperature to high temperature range and cools down from high temperature range to normal temperature have excellent thermal fatigue characteristics in order to maintain durability against the heat cycle. It becomes important. Examples of such a member include a vehicle exhaust gas member such as an exhaust manifold that comes into contact with the exhaust gas before the vehicle exhaust gas is discharged into the atmosphere. FIG. 1 schematically shows a stress-strain curve of a stainless steel material in one thermal cycle. In FIG. 1, the strain difference between two points where the generated stress is 0 is defined as an inelastic strain range. As the inelastic strain range becomes smaller, the amount of plastic deformation per one thermal cycle becomes smaller. As a result, the thermal fatigue characteristics are improved, that is, the steel material is hardly deteriorated even when exposed to a thermal cycle environment.

  By the way, in recent years, automobile exhaust gas regulations have become stricter due to increasing environmental problems, and it is necessary to further increase the fuel consumption of an automobile and the combustion efficiency of an engine. Therefore, the temperature of the automobile exhaust gas tends to rise to about 1000 ° C. at a high temperature. However, automobile exhaust gas members that are currently in practical use cannot obtain sufficient thermal fatigue characteristics at 1000 ° C. even if SUS444 steel having the best thermal fatigue characteristics is adopted. Therefore, a steel material that exhibits sufficiently excellent thermal fatigue characteristics even at a temperature of about 1000 ° C. or higher is desired.

Conventionally, in order to obtain such a steel material, attempts have been mainly made to reduce the inelastic strain range by adding a special element to steel and increasing the high-temperature strength. For example, in Patent Document 1, in order to reduce the thermal expansion coefficient in an Fe—Cr ferrite-based alloy, C: 0.03% or less, Mn: 5.0% or less, Cr: 6 to 40 in mass%. %, N: 0.03% or less, Si: 5% or less, W: 2.0% or more and 6.0% or less, precipitation W: 0.1% or less, the balance Fe and unavoidable impurities, Ferritic Cr-containing steel materials characterized by an average thermal expansion coefficient of 20 ° C. to 800 ° C. being smaller than 12.6 × 10 −6 / ° C. have been proposed.
JP 2005-206944 A

  However, simply adding a special element to the steel as proposed in Patent Document 1 only slightly improves the high-temperature strength at about 1000 ° C. In this case, the effect of improving the thermal fatigue characteristics is not sufficient, and it is inevitable that it is disadvantageous when comprehensively considering the material cost, workability, and low temperature toughness.

  Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a ferritic stainless steel material whose thermal fatigue characteristics are sufficiently improved as compared with the prior art.

  As a result of intensive studies to achieve the above object, the present inventors have thought that it is effective to reduce the thermal expansion by adding a large amount of Mo and Co to a ferritic stainless steel material. That is, the present inventors speculated that the inelastic strain range can be reduced by reducing the strain generated in the thermal cycle by reducing the thermal expansion, and the object of the present invention can be achieved. This concept can be represented by a stress-strain curve in a thermal cycle as shown in FIG.

  As a result of further detailed studies, the present inventors have found that low thermal expansion can be realized by adding a predetermined amount of Cr, Mo, Co to a ferritic stainless steel material to which Mo, Co is added. It was.

That is, the ferritic stainless steel material of the present invention has C: more than 0.000% by mass and 0.030% by mass or less, Si: more than 0.00% by mass and 1.00% by mass or less, Mn: more than 0.00% by mass 1 .50 mass% or less, Cr: 15.0 to 25.0 mass%, Mo: 1.00 to 4.00 mass%, Co: 1.00 to 5.00 mass%, N: more than 0.000 mass% A ferritic stainless steel material containing 0.030% by mass or less and the balance being composed of Fe and inevitable impurities, represented by the following formulas (1), (2), (3), and (4) One of the conditions is satisfied.
0.25 × W _Cr + 0.30 × W _Mo + 0.60 × W _Co ≧ 6.2 (W _Cr ≦ 20, W _Co ≦ 3.0) (1)
0.25 × W _Cr + 0.30 × W _Mo −0.10 × W _Co ≧ 4.1 (W _Cr ≦ 20, W _Co > 3.0) (2)
0.15 × W _Cr −0.30 × W _Mo −0.60 × W _Co ≦ 1.8 (W _Cr > 20, W _Co ≦ 3.0) (3)
0.15 × W _Cr −0.30 × W _Mo + 0.10 × W _Co ≦ 3.9 (W _Cr > 20, W _Co > 3.0) (4)
Here, in the formulas (1), (2), (3), and (4), W _Cr , W _Mo , and W _Co are the content ratios of Cr, Mo, and Co to the total mass of the ferritic stainless steel material ( (Unit: mass%).
The coefficient of the content ratio of each element in the above formulas (1) to (4) indicates the amount of change in the thermal expansion coefficient per 1% by mass of the element. By satisfying any one of the above formulas (1) to (4) within the range of each content ratio of Cr and Co, the thermal expansion coefficient of the ferritic stainless steel material can be increased. 11.5 × 10 ⁻⁶ / ° C. or less.

  Further, the ferritic stainless steel material of the present invention has Nb: more than 0.00 mass% and 0.80 mass% or less, Ti: more than 0.00 mass% and 0.40 mass% or less, and W: more than 0.00 mass%. It is preferable to further contain one or more elements selected from the group consisting of 3.00 mass% or less. Thereby, the ferritic stainless steel material of the present invention is further excellent in thermal fatigue characteristics.

The ferritic stainless steel material of the present invention preferably has a thermal expansion coefficient of 11.5 × 10 ⁻⁶ / ° C. or less between 30 ° C. and 1000 ° C.

  According to the ferritic stainless steel material of the present invention, the thermal fatigue characteristics can be sufficiently improved as compared with the prior art.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail.

First, the ferritic stainless steel material of the present embodiment (hereinafter, also simply referred to as “stainless steel material” or “steel material” in some cases) will be described. The ferritic stainless steel material of the present embodiment has C: more than 0.000% by mass and 0.030% by mass or less, Si: more than 0.00% by mass and 1.00% by mass or less, and Mn: more than 0.00% by mass. 50% by mass or less, Cr: 15.0 to 25.0% by mass, Mo: 1.00 to 4.00% by mass, Co: 1.00 to 5.00% by mass, N: more than 0.000% by mass 0 0.030% by mass or less, and the balance is a ferritic stainless steel material having a composition composed of Fe and inevitable impurities, and represented by the following formulas (1), (2), (3), and (4) One of the conditions is satisfied.
0.25 × W _Cr + 0.30 × W _Mo + 0.60 × W _Co ≧ 6.2 (W _Cr ≦ 20, W _Co ≦ 3.0) (1)
0.25 × W _Cr + 0.30 × W _Mo −0.10 × W _Co ≧ 4.1 (W _Cr ≦ 20, W _Co > 3.0) (2)
0.15 × W _Cr −0.30 × W _Mo −0.60 × W _Co ≦ 1.8 (W _Cr > 20, W _Co ≦ 3.0) (3)
0.15 × W _Cr −0.30 × W _Mo + 0.10 × W _Co ≦ 3.9 (W _Cr > 20, W _Co > 3.0) (4)
Here, in the formulas (1), (2), (3) and (4), W _Cr , W _Mo and W _Co are the content ratios of Cr, Mo and Co to the total mass of the ferritic stainless steel material ( (Unit: mass%).

  The ferritic stainless steel material of the present embodiment contains C and N in order to improve high temperature strength, particularly creep characteristics. However, the content ratio of C and N in the steel material is preferably more than 0.000 mass% and 0.030 mass% or less with respect to the total mass of the steel material, and the total content ratio thereof is 0.030 mass%. The following is more preferable. As a result, the oxidation characteristics, workability, low temperature toughness and weldability of the stainless steel material can be further improved, and in order to fix C and N, Ti and Nb which react with these to form carbonitrides. The amount added can be further reduced.

The ferritic stainless steel material of this embodiment contains Si from the viewpoint of suppressing high-temperature oxidation, particularly from the viewpoint of suppressing scale peelability. However, the content ratio (W _Si ) of _Si in the steel material is preferably more than 0.00 mass% and 1.00 mass% or less, and is 0.10 to 0.50 mass% with respect to the total mass of the steel material. And more preferred. Thereby, the workability of the steel material, in particular, the ductility can be more effectively prevented, and the low temperature toughness can be further effectively suppressed.

  The ferritic stainless steel material of the present embodiment contains Mn from the viewpoint of suppressing high-temperature oxidation, particularly from the viewpoint of suppressing scale peelability. However, the content ratio of Mn in the steel material is preferably more than 0.00% by mass and 1.50% by mass or less, and more than 0.00% by mass and 1.00% by mass or less with respect to the total mass of the steel material. More preferred. Thereby, the fall of workability and weldability of steel materials can be suppressed more. Further, since Mn is an austenite phase stabilizing element, when the Cr content is low, the addition of Mn promotes the formation of the martensite phase, and the thermal fatigue characteristics and workability are reduced. Also from the viewpoint of more effectively preventing the deterioration of the thermal fatigue characteristics and workability, it is preferable to adjust the content ratio of Mn in the steel material within the above range.

  The ferritic stainless steel material of the present embodiment contains Cr from the viewpoint of lowering its thermal expansion, that is, lowering the thermal expansion coefficient, stabilizing the ferrite phase, and enhancing the oxidation resistance regarded as important for high-temperature materials. To do. However, the content ratio of Cr in the steel material is 15.0 to 25.0 mass% with respect to the total mass of the steel material, and is preferably 18.0 to 23.0 mass%. Thereby, while steel material shows the further outstanding thermal fatigue characteristic, it can suppress the embrittlement and can prevent the fall of workability accompanying a raise of hardness more effectively.

  The ferritic stainless steel material of the present embodiment contains Mo from the viewpoint of ensuring excellent thermal fatigue characteristics at a high level. In order to make the thermal fatigue property of the steel material of this embodiment more excellent, the Mo content in the steel material is preferably 1.00% by mass or more with respect to the total mass of the steel material, and 1.50 mass. % Or more is more preferable. Moreover, the upper limit of the Mo content is preferably 4.00% by mass, and more preferably 3.00% by mass. Thereby, embrittlement of the steel material can be suppressed, and a decrease in workability accompanying an increase in hardness can be more effectively prevented. Moreover, it leads also to reduction of material cost.

  The ferritic stainless steel material of this embodiment contains Co from the viewpoint of ensuring excellent thermal fatigue characteristics at a high level. Co, like Cr and Mo, has an effect of suppressing the thermal expansion of the steel material, but its thermal expansion suppressing effect is much greater than that of Cr and Mo. From the viewpoint of achieving a thermal expansion suppressing effect at a higher level, the content ratio of Co in the steel material is 1.00% by mass or more and more preferably 2.50% by mass or more with respect to the total mass of the steel material. However, from the viewpoint of reducing the degree of improvement of the thermal expansion suppression effect and suppressing the material cost, the Co content is preferably 5.00% by mass or less, and more preferably 4.00% by mass or less. preferable.

The ferritic stainless steel material of the present embodiment may contain Nb from the viewpoint of increasing the high-temperature strength by forming carbonitride and fixing C and N. From the viewpoint of more effectively demonstrating this effect, the content ratio of Nb in the steel material is expressed by the following formula (5).
W _Nb ≧ 8 × (W _C + W _N ) (5)
It is preferable to satisfy the condition represented by. Here, in Formula (5), W _Nb , W _C , and W _N indicate the content ratio (unit: mass%) of Nb, C, and N, respectively, with respect to the total mass of the steel material. Nb that does not form carbonitride is effective in increasing the material strength of the steel material. However, the content ratio of Nb in the steel material is more than 0.00% by mass and greater than 0.80% by mass with respect to the total mass of the steel material from the viewpoint of suppressing the workability of the steel material, the low temperature toughness, and the decrease in sensitivity to welding hot cracking. Or less, more preferably more than 0.00% by mass and 0.50% by mass or less, and further more preferably more than 0.00% by mass and 0.30% by mass or less.

  The ferritic stainless steel material of the present embodiment preferably contains W from the viewpoint of increasing the strength at high temperatures and improving the strength from the middle temperature range to normal temperature. W combines with C to mainly form M23C6 type carbides, thereby producing the effects described above. However, the content ratio of W in the steel material is preferably more than 0.00 mass% and 3.00 mass% or less with respect to the total mass of the steel material. Thereby, embrittlement of the steel material can be suppressed, and a decrease in workability accompanying an increase in hardness can be more effectively prevented. Moreover, it can also contribute to reduction of material cost.

The ferritic stainless steel material of the present embodiment may contain Ti from the viewpoint of improving workability by forming carbonitride and fixing C and N. From the viewpoint of more effectively demonstrating this effect, the Ti content in the steel material is expressed by the following formula (6).
W _Ti ≧ 5 × (W _C + W _N ) (6)
It is preferable to satisfy the condition represented by. Here, in formula (6), W _Ti , W _C , and W _N indicate the content ratio (unit: mass%) of Ti, C, and N with respect to the total mass of the steel material. From the viewpoint of preventing the workability of the steel material from being reduced and reducing the material cost, the content ratio of Ti in the steel material is preferably more than 0.00 mass% and 0.40 mass% or less with respect to the total mass of the steel material. More preferably, it is more than 0.00 mass% and 0.30 mass% or less.

  The ferritic stainless steel material of this embodiment satisfies any of the conditions represented by the above formulas (1), (2), (3), and (4). By having such a composition, the steel material of the present embodiment can provide an excellent low thermal expansion and can provide a ferritic stainless steel material having sufficiently improved thermal fatigue characteristics. For example, Cr, Mo, and Co all contribute to reducing the thermal expansion coefficient of the steel material. Therefore, when the Cr and Co content ratios are in a certain range, the content ratio of these elements is increased so as to satisfy the condition expressed by the above formula (1), and the thermal expansion coefficient of the steel material is lowered. On the other hand, when Co is contained excessively, the thermal expansion coefficient of the steel material tends to increase. Therefore, in the range where the Co content ratio is higher than that in the above formula (1), the content of Mo and Cr is suppressed while suppressing the Co content ratio so as to satisfy the condition represented by the above formula (2). Increasing the ratio suppresses the increase in the thermal expansion coefficient of the steel material. Similarly, the conditions represented by the above formulas (3) and (4) also consider comprehensively low thermal expansion and high thermal expansion due to the addition of Mo and Co in a range where the content ratios of Cr and Co are respectively constant. Is set.

  In addition to the above elements, the ferritic stainless steel material of the present embodiment may contain, for example, general impurity elements such as P, S, and O. However, the content is preferably as small as possible. The content ratios of P, S, and O in the steel material are preferably 0.040% by mass or less, 0.030% by mass or less, and 0.020% by mass or less, respectively, with respect to the total mass of the steel material. However, in order to further improve the workability and toughness of the steel material of this embodiment, these elements may be further reduced. Further, the ferritic stainless steel material of the present embodiment includes Zr, Y, REM (rare earth elements) that are elements that improve heat resistance, and Ca, Mg, and B that are elements that improve hot workability. As long as it does not impede the purpose, it may be contained if necessary.

In the ferritic stainless steel material of the present embodiment, the coefficient of thermal expansion between 30 ° C. and 1000 ° C. can be adjusted to 11.5 × 10 ⁻⁶ / ° C. or less by adjusting the composition of each element within the above range. it can. As a result, the ferritic stainless steel material of the present embodiment has long-term excellent thermal fatigue characteristics even when exposed to an environment where the thermal cycle is repeated in a temperature range from room temperature to a high temperature exceeding 1000 ° C. Can be held over the entire area. The thermal expansion coefficient is 4 mm × 4 mm × 50 mm plate-shaped test piece heated to 30 ° C. to 1000 ° C. at a temperature rising rate of 1 ° C./second with a differential expansion analyzer (standard sample: quartz). It is a value calculated as an average coefficient of thermal expansion at 30 ° C. to 1000 ° C. by measuring the amount of expansion of the test piece.

  Moreover, the ferritic stainless steel material of this embodiment can make 0.2% yield strength in 1000 degreeC 11.0 Mpa or more by adjusting the composition of each element in the above-mentioned range. As a result, it is possible to further increase the high temperature strength and obtain better thermal fatigue characteristics. The 0.2% proof stress is a value measured according to JIS G 0567.

  The ferritic stainless steel material of the present embodiment described above can be manufactured by a conventional method except having the above composition. Further, this steel material may be formed and processed into a predetermined shape such as a plate shape by a conventional method.

The ferritic stainless steel material of this embodiment is the first result of the present inventors' investigation of a rational component design to sufficiently improve thermal fatigue characteristics by reducing thermal expansion without increasing the high temperature strength more than necessary. It has been completed. Since the ferritic stainless steel material of the present embodiment has the above-described composition, the thermal expansion coefficient between 30 ° C. and 1000 ° C. can be adjusted to 11.5 × 10 ⁻⁶ / ° C. or less. As a result, this steel material exhibits better thermal fatigue properties than conventional steel materials such as SUS444 steel.

  The ferritic stainless steel material of the present embodiment is particularly suitably used for a member that is exposed to a heat cycle environment between a high temperature range where the maximum temperature exceeds 1000 ° C. and normal temperature. Such an application includes an automobile exhaust gas member, and an exhaust manifold is particularly preferable. Other uses include, for example, automobile and motorcycle exhaust gas path members such as catalytic converter cases and front pipes, and various exhaust gas path members such as LNG power generation ducts, micro gas turbines, fuel cell reformers, and gas heat pumps.

  The best mode for carrying out the present invention has been described above, but the present invention is not limited to this embodiment. The present invention can be variously modified without departing from the gist thereof.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
<Preparation of ferritic stainless steel specimen>
21 types of stainless steel (steel Nos. 1 to 21) having the compositions shown in Table 1 were melted in a vacuum melting furnace and cast into a 30 kg ingot. The obtained ingot was hot-rolled and further annealed at 1050 ° C. to obtain a ferritic stainless hot-rolled annealed plate having a thickness of about 4.5 mm. The obtained hot-rolled annealed plate was cut into a plate shape of 4 mm × 4 mm × 50 mm to obtain a test piece for measuring the thermal expansion coefficient. Further, the hot-rolled annealed plate was subjected to cold rolling and finish annealing to produce a cold-rolled annealed plate having a thickness of 2.0 mm and subjected to a high temperature tensile test. Further, a cylinder having a diameter of about 25 mm was produced from the ingot by hot forging, and finish annealing was performed at 1050 ° C. on the cylinder to obtain a test piece for a thermal fatigue test. In Table 1, “calculated value” is a calculated value using any one of the left sides of the formulas (1), (2), (3), and (4), and the formula used is shown in the “formula” column. In addition, comparative steel No. 14 is a steel material equivalent to SUS444 steel.

<Measurement of thermal expansion coefficient>
The plate-shaped test piece obtained as described above was heated at a heating rate of 1 ° C./second using a differential expansion analyzer (manufactured by Rigaku Corporation, infrared heating thermal expansion measuring device (TMA), standard sample: quartz). Heated to 30-1000 ° C. The amount of expansion of the test piece at that time was measured and calculated as an average thermal expansion coefficient (α _{30-1000 ° C.} ) at 30 ° C. to 1000 ° C. The results are shown in Table 2.

<Tensile test>
The cold-rolled annealed plate obtained by finish annealing as described above was again heated to 1050 ° C. and then cooled at a cooling rate of about 3 ° C./second. About the test piece after cooling, based on JISG0567, the 0.2% yield strength ((sigma) _{1000 degreeC} ) in ₁₀₀₀ degreeC was measured. The results are shown in Table 2.

<Thermal fatigue test>
The cylindrical specimen having a diameter of about 25 mm obtained as described above was further processed into a thermal fatigue specimen having a diameter of 10 mm between the gauge points. Using a servo pulsar type thermal fatigue test apparatus (manufactured by Shimadzu Corporation, trade name “EHF-EM 100 kN”), a thermal fatigue test was performed by exposing to a thermal cycle in the atmosphere under a binding force of 50%. The heat cycle was started from 200 ° C. to 1000 ° C. at a temperature increase rate of 3 ° C./second, held at 1000 ° C. for 0.5 minutes, then cooled to 200 ° C. at a cooling rate of 3 ° C./second, and 0 ° C. at 200 ° C. The cycle for 5 minutes was defined as one cycle. This thermal cycle was repeated 10 times, a stress-strain curve at that time was created, and the inelastic strain range (Δεp _{200-1000 ° C.} ) of the 10th cycle was derived. The results are shown in Table 2.

  Steel according to the present invention (invention steel) No. Nos. 1 to 13 are comparative steel No. 1 corresponding to SUS444 steel. The strength at high temperature was lower than 12. However, these inventive steels exhibited excellent thermal fatigue properties because they had a smaller coefficient of thermal expansion than the comparative steels. On the other hand, Comparative Steel No. Comparative steel No. 14 with a smaller thermal expansion coefficient than No. 14 Nos. 15-18 have a large thermal expansion coefficient and a large inelastic strain range despite the fact that the 0.2% proof stress at 1000 ° C. is lower than that of the inventive steel. The effect was not recognized. Comparative steel No. In 19-21, the 0.2% proof stress at 1000 ° C. was equivalent to that of the inventive steel, but the effect of improving the thermal fatigue characteristics was not recognized.

It is a schematic diagram of the stress-strain curve of the stainless steel material in one thermal cycle of a thermal fatigue test. It is a schematic diagram of the stress-strain curve of the conventional and the stainless steel materials according to the present invention in one thermal cycle of the thermal fatigue test.

Claims (3)

C: more than 0.000% by mass and 0.030% by mass or less, Si: more than 0.00% by mass and 1.00% by mass or less, Mn: more than 0.00% by mass and 1.50% by mass or less, Cr: 15.0 -25.0 mass%, Mo: 1.00-4.00 mass%, Co: 1.00-5.00 mass%, N: more than 0.000 mass% and 0.030 mass% or less, and the balance Is a ferritic stainless steel material having a composition consisting of Fe and inevitable impurities,
A ferritic stainless steel material that satisfies any of the conditions represented by the following formulas (1) to (4).
0.25 × W _Cr + 0.30 × W _Mo + 0.60 × W _Co ≧ 6.2 (W _Cr ≦ 20, W _Co ≦ 3.0) (1)
0.25 × W _Cr + 0.30 × W _Mo −0.10 × W _Co ≧ 4.1 (W _Cr ≦ 20, W _Co > 3.0) (2)
0.15 × W _Cr −0.30 × W _Mo −0.60 × W _Co ≦ 1.8 (W _Cr > 20, W _Co ≦ 3.0) (3)
0.15 × W _Cr −0.30 × W _Mo + 0.10 × W _Co ≦ 3.9 (W _Cr > 20, W _Co > 3.0) (4)
(In the formulas (1), (2), (3), (4), W _Cr , W _Mo , W _Co are the content ratios of Cr, Mo, Co to the total mass of the ferritic stainless steel material (unit: Mass%).)   Nb: more than 0.00% by mass and 0.80% by mass or less, Ti: more than 0.00% by mass and 0.40% by mass or less, and W: more than 0.00% by mass and 3.00% by mass or less. The ferritic stainless steel material according to claim 1, further comprising at least one kind of element. 3. The ferritic stainless steel material according to claim 1, wherein a coefficient of thermal expansion between 30 ° C. and 1000 ° C. is 11.5 × 10 ⁻⁶ / ° C. or less.

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